1. Field of the Invention (Technical Field)
The present invention relates to an improved copper-inducible promoter system in yeast for the controlled expression of recombinant genes.
2. Background Art
Inducible promoters that can provide precise temporal control over transgene expression are widely used to investigate recombinant gene functions. The copper-inducible gene expression system from Saccharomyces cerevisiae was first successfully introduced into tobacco by Mett et al. (Proc. Natl. Acad. Sci. USA 90:4567-4571 (1993)), which is incorporated herein by reference. This system consists of two elements: (i) the yeast activating copper-element (ace I) gene encoding copper-responsive transcription factor ACE1, and (ii) the metal responsive element (MRE) containing ACE1-binding sites. When copper(II)-ion binds to transcription factor ACE1, the ion alters the protein's conformation thereby promoting binding of the protein to the MRE, which then triggers the transcription of a target gene ligated downstream from the MRE.
The benefit of the copper-inducible system is that it does not interfere with the normal physiology of the affected organism. However, the system has not been consistently successful. Therefore, there is a need for an effective copper-inducible promoter system.